1. Field of the Invention
The present invention relates to wheels having extendable traction spikes and to toys which include such wheels. More specifically, the wheels of the present invention have a plurality of traction spikes called spike pins which are contained within the wheel and, in response to either a predetermined movement or achievement of a predetermined torque, the spike pins are automatically extended to enhance wheel traction.
2. Prior Art Statement
There are many hundreds of patents directed to traction enhancing spikes for wheels, but none have been found to teach the unique features of the present invention whereby the spike pins are automatically extended to enhance traction in response to a predetermined movement or to an attainment of a predetermined torque level. Exemplary of this prior art are the following patents:
U.S. Pat. No. 756,395 to J. P. McEwing describes a traction wheel which includes spikes (called "cleats") disposed within slots in the wheel and which extend out by contact of guide wheels at the end of each spike with an eccentric cam. Unlike the present invention wheel, the spikes of McEwing extend out for ground traction independent of whether or not the wheel is moving and independent of achievement of a predetermined level of torque. Also, the functional elements are different and operate differently.
U.S. Pat. No. 1,308,513 to F. Voegeli teaches a traction wheel which includes a plurality of traction members which are pivotably attached at one end to the wheel rim and can swing out and be locked in a traction enhancing position. Hand operation is required to lock each traction member and automatic extension is not taught nor are any of the elements of the present invention.
U.S. Pat. No. 1,702,617 to P. Pfeifer describes a tractor wheel with adjustable lugs for increased traction. Again, hand operation is required and none of the essential elements of the present invention are taught.
U.S. Pat. No. 1,890,872 to L. S. Van Kleeck illustrates an antiskid device which includes spikes which are attached to a disc which may be fitted to a wheel hub. The spikes are connected to a two position bowed carrier for retraction or extension of the spikes as may be desired. Hand operation of a spring-anchored member requires the use of a wrench or tool.
U.S. Pat. No. 1,997,835 to F. H. Sandherr describes a tractor wheel with traction spikes which retract and extend due to the eccentric position of the flange, resulting in the ground contact spikes being extended and the spikes away from the ground being partially or fully retracted. Whether or not a particular spike is extended depends only on its position on the wheel relative to the ground and does not depend upon whether or not there is movement or attainment of torque.
U.S. Pat. No. 2,714,042 to E. E. Kelly describes a traction attachment for wheels which is designed to be bolted adjacent to a wheel. It has spikes which extend or retract in response to rotation of a slotted cam plate. This must be done manually (two hand grips are provided). The spikes respond only to manual rotation of the cam plate and do not extend in response to wheel motion or torque.
U.S. Pat. No. 3,712,359 to Victor E. Williams describes "crazy tires" which have spikes or bumps inside a tire. These do not extend and none of the elements of the present invention are taught.
U.S. Pat. No. 4,266,832 to Antoine Delauney and Michael Boyer teaches a vehicle wheel anit-slip device whereby blades are extended through the wheel by actuation of a roller manually or by hydraulic jack. Again, the present invention elements are not taught nor are the same objectives achieved.